fuel pressure to run in mr2

[touge rolla]

what pressure should i set my fuel pressure regulator to????

[vvega]

39.5 psi

[92mr2paddy]

hi, im thinking of putting a fuel reg on my mr2 turbo as well.. if i install a fuel reg will that increase the potential of the standard injectors?? or will i still need bigger injecters (going to run a highflowed ct20b)

[vvega]

hi, im thinking of putting a fuel reg on my mr2 turbo as well.. if i install a fuel reg will that increase the potential of the standard injectors?? or will i still need bigger injecters (going to run a highflowed ct20b)

if you raise teh fuel pressure toyr injectors will flow more......but your ecu wont beabile to compensate so you will just run richer.....

a lot of cheaper fuel pressure regs atually cause more problemns than they solve .....pressure spikes etc.... the factory one is atually pritty friggin good :d

v

[92mr2paddy]

ok, when i get all this set up going i will be running a Link G3 anyway, i want to stay away from changing the injectors since they around 600-800 themselves. so the fuel pressure reg is the way to go if upgrading the system with a link comp and ct20b?

[Dell'Orto]

That'll help, but unless you're planning on trying to run idiotic boost, it should be fine. Most MR2's sem to run quite rich, even with 17-18psi on CT20B's.

[sergei]

you will not gain much of the fuel flow by increasing the pressure.
To get 440cc injectors flowing close to 600cc you will need to increase fuel pressure almost twice. That providing if injectors are able to open at that pressure.

[fivebob]

You're not going to get much of an increase, and the stock Gen II fuel system is enough to extract 280RWHP so it's not really worth doing. Save your money for bigger injectors .

FWIW the specs on the Gen 2 injectors are
410cc/min@2.55Bar(37psi)
455cc/min@3.05Bar(44psi)
490cc/min@3.55Bar(51.5psi)

[sergei]

here is formula:

New Flow = Old Flow times Square Root of ( New Pressure divided by Old Pressure).

[RedMist]

Dont they run a rising rate FPR stock? (its been a long while since I've touched a bluetop or redtop bigport). IE putting a single rate FPR will screw the maps.

[fivebob]

Dont they run a rising rate FPR stock? (its been a long while since I've touched a bluetop or redtop bigport). IE putting a single rate FPR will screw the maps.

No, they run a fixed pressure differential regulator. i.e. fuel pressure is always the same amount above manifold pressure. Rising rate regulators are a PITA to tune and I don't know why anyone would want to use them.

[vvega]

ok, when i get all this set up going i will be running a Link G3 anyway, i want to stay away from changing the injectors since they around 600-800 themselves. so the fuel pressure reg is the way to go if upgrading the system with a link comp and ct20b?

upgrading teh fuel pressure reg to a better quality one gives you better fuel control
its a fas to raise the pressure to tri to get a little more out of injectors buy raising teh fuel pressure

the more you increase your pressure teh less yoru fuel pump flows....
so its really just takign from peter to give to paul

your stock fuell system will more than coape with the ct20b requirements
for under say 18 ish psi
anythign over that and your just asking for things to go bang

[RedMist]

Dont they run a rising rate FPR stock? (its been a long while since I've touched a bluetop or redtop bigport). IE putting a single rate FPR will screw the maps.

No, they run a fixed pressure differential regulator. i.e. fuel pressure is always the same amount above manifold pressure. Rising rate regulators are a PITA to tune and I don't know why anyone would want to use them.

So the fuel pressure rises and falls with manifold pressure? The ECU is expecting this change in pressure? So by fixing the fuel pressure, you're screwing the maps?

[fivebob]

So the fuel pressure rises and falls with manifold pressure? The ECU is expecting this change in pressure? So by fixing the fuel pressure, you're screwing the maps?

The reason for this change in pressure is to keep the fuel flow constant regardless of manifold pressure. By keeping the differential between manifold and fuel rail pressure the same, the flow rate of the injectors doesn't change, so fuel delivered is only dependent of inkector opening times.

I don't know of any FPR's (except extremely cheap ones that no one in their right mind would use) that don't have a manifold pressure reference.

Rising rate FPR's are a different thing altogether, they increase the pressure differential as the manifold pressure rises, therefore deliver more fuel for the same injector open times at higher manifold pressures.

[RomanV]

I don't know of any FPR's (except extremely cheap ones that no one in their right mind would use) that don't have a manifold pressure reference.

Mine doesnt!

Standard toyota gen 4 3S.

My FPR has a 'vaccuum' hose coming from it, but it doesnt actually connect onto the manifold where there's vaccuum... it connects onto the throttle body, strangely enough.

I asked a few other people with the same engine to check, and it's definitely like this from factory... There's nowhere else for it to go!

[fivebob]

I don't know of any FPR's (except extremely cheap ones that no one in their right mind would use) that don't have a manifold pressure reference.

Mine doesnt!

Standard toyota gen 4 3S.

My FPR has a 'vaccuum' hose coming from it, but it doesnt actually connect onto the manifold where there's vaccuum... it connects onto the throttle body, strangely enough.

I asked a few other people with the same engine to check, and it's definitely like this from factory... There's nowhere else for it to go!

Yes, but which side of the throttle plate does the hole go to?

[vvega]

I don't know of any FPR's (except extremely cheap ones that no one in their right mind would use) that don't have a manifold pressure reference.

Mine doesnt!

Standard toyota gen 4 3S.

My FPR has a 'vaccuum' hose coming from it, but it doesnt actually connect onto the manifold where there's vaccuum... it connects onto the throttle body, strangely enough.

I asked a few other people with the same engine to check, and it's definitely like this from factory... There's nowhere else for it to go!

just for intest..if tuning via tps its adviced to just run a base pressure
fivebob my iunderstanding is that any fpr that changed pressure is rising rate

just some have a different ratio i.e 1:3 1psi of mani presure = 3psi od fuel pressure....vrs 1:1 1psi of boost for one psi of fuel pressure


certanly aeromotive call there 1:1 versions rising rate as well

N/A cars dont need to have then david
F/I cars need them so that at 40psi of boost you still get fuel commin out

purely as fivebob said maintains the pressure differental

[Akane]

The rising rate FPR's (1:1.25 etc) were popular around the Honduh boys when they turbo their "mean azz H22A VTAX au" engines. I don't know why they would want to use one, I couldn't be bothered finding out why.

Even a factory turbo car FPR will do unless you're trying to "extract" more from your injectors.

[fivebob]

just for intest..if tuning via tps its adviced to just run a base pressure

That's true, except if you have idle speed control that does not alter the throttle plate angle, then you connect it to the manifold to ensure that the AFR doesn't change.

fivebob my iunderstanding is that any fpr that changed pressure is rising rate

just some have a different ratio i.e 1:3 1psi of mani presure = 3psi od fuel pressure....vrs 1:1 1psi of boost for one psi of fuel pressure


certanly aeromotive call there 1:1 versions rising rate as well

I always understood that rising rate refered to the rate of fuel delivery not to any pressure increase. But like most terms I'm sure it means different things to different people. I'll continue to refer to anything that changes the rate of fuel delivery as a rising rate regulator, and one that just maintains the pressure differential as a constant rate FPR

N/A cars dont need to have then david

True, but sometimes it's desirable to have them, i.e. when running large injectors to allow a longer pulsewidth at idle.

[vvega]

agreed completly

BTW any hints to get my 800's to idle nicely

v